Frequency tuning of a squeezed vacuum state using interferometric enhanced Bragg diffraction effect

We experimentally demonstrate the optical frequency tuning of a squeezed vacuum state generated from an optical parametric oscillator by using an acousto-optic modulator based bi-frequency interferometer. The systematic efficiency of the frequency tuning device is $91\%$, which is only confined by the optical transmission efficiency of the acousto-optic modulators. The amount of frequency tuning is 80 MHz, which is orders of magnitude larger than the line-width of the laser used to generate the squeezed state, and can in principle be further extended to GHz range. Our investigation shows the interferometric enhanced Bragg diffraction effect can be applied to a variety of other quantum optical states as well, and will serve as a handy tool for quantum network.